Financial Instruments and Hedging Activities (Details) (USD $)							6 Months Ended
	Sep. 30, 2012	Mar. 31, 2012	Sep. 30, 2012 Fair Value, Inputs, Level 1 [Member] Money Market Funds [Member]	Mar. 31, 2012 Fair Value, Inputs, Level 1 [Member] Money Market Funds [Member]	Sep. 30, 2012 Fair Value, Inputs, Level 2 [Member]	Mar. 31, 2012 Fair Value, Inputs, Level 2 [Member]	Sep. 30, 2012 Designated as Hedging Instrument [Member]	Mar. 31, 2012 Designated as Hedging Instrument [Member] Fair Value, Inputs, Level 2 [Member]	Mar. 31, 2012 Not Designated as Hedging Instrument [Member] Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market fund investments			$ 1,100,000,000	$ 800,000,000
Long-term debt and other financing, carrying value	3,600,000,000	3,600,000,000
Long-term debt and other financing, fair value					4,200,000,000	4,100,000,000
Maturity Period, Years							8 years
Notional Amount of Foreign Currency Derivatives								$ 528,000,000	$ 151,000,000